Juvenile experience and learning events in humans modulate the functional maturation of the brain, thereby shaping the neuronal substrate for the development of intellectual and socio-emotional abilities. Animal models have provided useful testable conceptual and comparative frameworks applicable to studies of human infants and vice versa. Scaffolding behavior and opportunity teaching are important processes in the development of language and technical skill acquisition in young children. The proposed study will explore the function of opportunity teaching and maternal or parental scaffolding and the influence of social dynamics on complex skill acquisition and behavioral performance in sub-adults in two species of primates: 1) captive cotton-top tamarins on a simulated naturalistic foraging task and 2) wild chimpanzees on a hazardous tool use task. In addition, to shed light on the evolution of social learning in human and non-human primates, associated costs to social learning will be investigated in relation to behavioral efficiency and environmental variability. In the chimpanzees, video data will be gathered from the wild and a semi-controlled natural outdoor laboratory setting; while, data on the tamarins will be obtained through a series of experiments with control and baseline trials in captivity. [unreadable] [unreadable]